I have been lately working on the upgrade of one of my Exchange 2013 servers to CU5.
My installation attempt was interrupted with a lot of errors and warnings which were revealed during prerequisites check.
The good things is that all these warnings are quite straightforward and therefore are really addressable.
The first warning was very straight forward: send connector with the namespace * was missing e.g. your Exchange organization is not able to send email to the internet. This can be ignored (which is not fatal) and the send connector can be configured afterwards or you can run this command to have the connector created:
New-SendConnector "Internet Send Connector" -FrontendProxyEnabled:$true -AddressSpaces *
The second warning was about missing UCMA 4.0. I was surprised how Exchange 2013 was there in the first place without it. But I ended up downloading and installing it. Which again is very straight forward.
Finally there was an error related to the UM services not being able to be installed because of misconfigured PowerShell execution policy.
It can be found at this branch: Computer Policy-> User Configuration-> Administrative Templates-> Windows Components-> Windows PowerShell. The setting name is Turn On Script Execution. The default setting of the is Enabled for all scripts.
To make UM installation successful we need to enable it. Following instructions for from MS support article I have set the value for Turn On Script Execution to Not Configured.
After this I have executed setup.exe /m:Upgrade /IAcceptExchangeServerLicenseTerms and Exchange 2013 upgrade to SP1 has gone smoothly.
So the main trick here is to read warnings and use the appropriate URLs.